The present invention relates generally to a method and apparatus for allocating static inverters to a load and, in particular, to a method and apparatus for controlling the share of the load for each static inverter.
There is shown in the Swiss patent specification 682 531 a method by which static inverters are connected in parallel to feed electrical power to a load. A main regulator determines when the upper and lower switches of all partial static inverters must be switched on or off together from a comparison of the total output current of the parallel connected static inverters with the current target value. This switching instant is preset for the individual static inverters as a target value. Each static inverter has the ability to vary the exact instant for its switching in a small range, a time window, and thus to bring about a current equalization. Defective units can be disconnected during operation. Additional static inverters can be switched in or out during operation in order to adapt to different load states.
In the aforedescribed method, the static inverters are connected in parallel in order to feed a load. There is the possibility that the time window allows switches to close before the time zero point or open after the time zero point. Thereby, a hot path is formed between the corresponding switches of the partial static inverters. A static inverter switched away from the load cannot be used for the feeding of a further load.